Computer input devices for the input of coordinates and graphic information in a computer typically utilize a mouse and trackball. Such input devices contain a trackball that generates a signal which corresponds to a position angle and two covers. A positioner is typically located between the covers in a such manner that it is only partially raised behind the covers. One of the covers is hinged and is able to move between a closed and open position. A retainer is used to hold the covers in a position that ensures that the positioner is held against a flat surface. A second retainer is typically used to hold both covers in such location and manner that the surface of the positioner is supported by two surface and in contact with the flat surface.
The disadvantage of these devices is that it they are limited to controlling only two coordinates, X and Y. Additionally, the device typically requires a special work surface for the device movement, and the parts and assemblies for the device must be manufactured to precise mechanical specifications. Furthermore, the device may easily fail as a result of wear and dust accumulation on the moving parts.
Graphic positioners that provide input for 3 independent coordinates, X, Y, and Z, typically consist of a base with two perpendicular shafts rotating in sets of bearings and a third shaft that is mounted on a bezel in a bearing assembly. Each shaft is mated to a coder that translates the shaft rotation into code. The code is supplied through a cable to the computer in order to control a graphic object on a display.
This device is also limited to controlling one pair of coordinates at a time, (XY), or (XZ), or (YZ). Furthermore, the device typically provides an uncomfortable position for the operator's wrist and a rigidly limited area in which the operator's hand must be located during the manipulations (determined by the shaft's length, where shaft is fixed in a holder and on a base). In addition, the device contains of parts that are difficult to manufacture and are prone to excessive wear due to friction.
Another type of controller for providing three-dimensional input data is a device that has a coordinating handle. This controller typically contains a spheroid inside a stationary casing which freely rotates in all directions. Attached to the spheroid is a handle that can be rotated and moved in any direction. The device also contains inner and outer leverage plates that are attached by hinges to the casing. These leverage plates typically align at intersection planes and rotate simultaneously with the handle. Two angle converters are attached to the casing and driven by rotation of the plate. The rotational angle converter is also typically driven by the handle rotation. Depending on the axial movement of the handle, the rotational angle converter is typically connected or disconnected from the handle by a coupling clutch installed between them. The handle rotation produces electrical signals on the device's output.
The disadvantage of this type of controller is the complex design of the rotating handle. A large number of parts and assemblies require precision machining. Further, a large number of parts are susceptible to wear which will reduce the life of the device.
Another type of input device is a computer-input pen designed for input of handwritten information. The pen consists of a hollow casing with a writing element having acceleration and pressure sensors. Typically, the acceleration and pressure sensors are mutually perpendicular piezoelectric plates with inertial elements that are placed along the axis of the writing element in two rows. The upper row consists of inertial sensors attached to the lower edges of the piezoelectric plates. These piezoelectric plates are typically parallel to the axis of the writing element. One edge of the piezoelectric plates is rigidly attached to the casing while the other edge is attached to the writing element through the spring-loaded rod. This device only allows for two-dimensional coordinate input of information into computer.
There is a need for a data input device that is easy to manufacture can provide manipulations in six degrees of freedom, and is capable of gradual adjustment.